The forums he is having trouble in are Classic, he may see this one as Zeta and that could be the difference. If he's using and MS browser it could either have compatibility setting enabled (for IE) or there's something new with Edge and Classic we are not aware of OR like you said, a security feature is not allowing the editor to load.

If you do not use bookmarks, something else to try is deleting your Delphi cookies. Make sure you know your password (if you do not you can ask it to email you a new one, if all heck break loose and you loose your password AND it's not emailing you the correct one you can write to service@delphiforums.com and put Need Password in the subject line. ) Then follow the above instructions for login in. Your browser will save new cookies.

If ALL that fails to help (first off - thank you for trying!) take a look at your browser addons - you might even want to try that first if you recall recently adding something.

I'll email you a copy of this post as well. Keep my email address handy in case you get lost some how.